export const forEach = (arr, fn) => {
    if (!arr.length || !fn) return;
    let i = -1;
    let len = arr.length;
    while (++i < len) {
        let item = arr[i];
        fn(item, i, arr);
    }
};

/**
 * @param {Array} arr1
 * @param {Array} arr2
 * @description 得到两个数组的交集, 两个数组的元素为数值或字符串
 */
export const getIntersection = (arr1, arr2) => {
    let len = Math.min(arr1.length, arr2.length);
    let i = -1;
    let res = [];
    while (++i < len) {
        const item = arr2[i];
        if (arr1.indexOf(item) > -1) res.push(item);
    }
    return res;
};

/**
 * @param {Array} arr1
 * @param {Array} arr2
 * @description 得到两个数组的并集, 两个数组的元素为数值或字符串
 */
export const getUnion = (arr1, arr2) => {
    return Array.from(new Set([...arr1, ...arr2]));
};

/**
 * @param {Array} target 目标数组
 * @param {Array} arr 需要查询的数组
 * @description 判断要查询的数组是否至少有一个元素包含在目标数组中
 */
export const hasOneOf = (target, arr) => {
    return target.some(_ => arr.indexOf(_) > -1);
};

/**
 * @param {String|Number} value 要验证的字符串或数值
 * @param {*} validList 用来验证的列表
 */
export function oneOf(value, validList) {
    for (let i = 0; i < validList.length; i++) {
        if (value === validList[i]) {
            return true;
        }
    }
    return false;
}

/**
 * @param {Number} timeStamp 判断时间戳格式是否是毫秒
 * @returns {Boolean}
 */
const isMillisecond = timeStamp => {
    const timeStr = String(timeStamp);
    return timeStr.length > 10;
};

/**
 * @param {Number} timeStamp 传入的时间戳
 * @param {Number} currentTime 当前时间时间戳
 * @returns {Boolean} 传入的时间戳是否早于当前时间戳
 */
const isEarly = (timeStamp, currentTime) => {
    return timeStamp < currentTime;
};

/**
 * @param {Number} num 数值
 * @returns {String} 处理后的字符串
 * @description 如果传入的数值小于10，即位数只有1位，则在前面补充0
 */
const getHandledValue = num => {
    return num < 10 ? '0' + num : num;
};

/**
 * @param {Number} timeStamp 传入的时间戳
 * @param {Number} startType 要返回的时间字符串的格式类型，传入'year'则返回年开头的完整时间
 */
const getDate = (timeStamp, startType) => {
    const d = new Date(timeStamp * 1000);
    const year = d.getFullYear();
    const month = getHandledValue(d.getMonth() + 1);
    const date = getHandledValue(d.getDate());
    const hours = getHandledValue(d.getHours());
    const minutes = getHandledValue(d.getMinutes());
    const second = getHandledValue(d.getSeconds());
    let resStr = '';
    if (startType === 'year') resStr = year + '-' + month + '-' + date + ' ' + hours + ':' + minutes + ':' + second;
    else resStr = month + '-' + date + ' ' + hours + ':' + minutes;
    return resStr;
};

/**
 * @param {String|Number} timeStamp 时间戳
 * @returns {String} 相对时间字符串
 */
export const getRelativeTime = timeStamp => {
    // 判断当前传入的时间戳是秒格式还是毫秒
    const IS_MILLISECOND = isMillisecond(timeStamp);
    // 如果是毫秒格式则转为秒格式
    if (IS_MILLISECOND) Math.floor(timeStamp /= 1000);
    // 传入的时间戳可以是数值或字符串类型，这里统一转为数值类型
    timeStamp = Number(timeStamp);
    // 获取当前时间时间戳
    const currentTime = Math.floor(Date.parse(new Date()) / 1000);
    // 判断传入时间戳是否早于当前时间戳
    const IS_EARLY = isEarly(timeStamp, currentTime);
    // 获取两个时间戳差值
    let diff = currentTime - timeStamp;
    // 如果IS_EARLY为false则差值取反
    if (!IS_EARLY) diff = -diff;
    let resStr = '';
    const dirStr = IS_EARLY ? '前' : '后';
    // 少于等于59秒
    if (diff <= 59) resStr = diff + '秒' + dirStr;
    // 多于59秒，少于等于59分钟59秒
    else if (diff > 59 && diff <= 3599) resStr = Math.floor(diff / 60) + '分钟' + dirStr;
    // 多于59分钟59秒，少于等于23小时59分钟59秒
    else if (diff > 3599 && diff <= 86399) resStr = Math.floor(diff / 3600) + '小时' + dirStr;
    // 多于23小时59分钟59秒，少于等于29天59分钟59秒
    else if (diff > 86399 && diff <= 2623859) resStr = Math.floor(diff / 86400) + '天' + dirStr;
    // 多于29天59分钟59秒，少于364天23小时59分钟59秒，且传入的时间戳早于当前
    else if (diff > 2623859 && diff <= 31567859 && IS_EARLY) resStr = getDate(timeStamp);
    else resStr = getDate(timeStamp, 'year');
    return resStr;
};

/**
 * @returns {String} 当前浏览器名称
 */
export const getExplorer = () => {
    const ua = window.navigator.userAgent;
    const isExplorer = (exp) => {
        return ua.indexOf(exp) > -1;
    };
    if (isExplorer('MSIE')) return 'IE';
    else if (isExplorer('Firefox')) return 'Firefox';
    else if (isExplorer('Chrome')) return 'Chrome';
    else if (isExplorer('Opera')) return 'Opera';
    else if (isExplorer('Safari')) return 'Safari';
};

/**
 * @description 绑定事件 on(element, event, handler)
 */
export const on = (function () {
    if (document.addEventListener) {
        return function (element, event, handler) {
            if (element && event && handler) {
                element.addEventListener(event, handler, false);
            }
        };
    } else {
        return function (element, event, handler) {
            if (element && event && handler) {
                element.attachEvent('on' + event, handler);
            }
        };
    }
})();

/**
 * @description 解绑事件 off(element, event, handler)
 */
export const off = (function () {
    if (document.removeEventListener) {
        return function (element, event, handler) {
            if (element && event) {
                element.removeEventListener(event, handler, false);
            }
        };
    } else {
        return function (element, event, handler) {
            if (element && event) {
                element.detachEvent('on' + event, handler);
            }
        };
    }
})();
